Re: [PATCH net-next] netlink: specs: add big-endian byte-order for u32 IPv4 addresses

[Hangbin Liu <liuhangbin@gmail.com>]

On Wed, Nov 26, 2025 at 01:32:22PM +0000, Asbjørn Sloth Tønnesen wrote:
> On 11/26/25 6:36 AM, Hangbin Liu wrote:
> > Hi,
> > On Tue, Nov 25, 2025 at 05:03:13PM +0000, Asbjørn Sloth Tønnesen wrote:
> > > I also checked how consistently defined the fields using the ipv6 display helper are,
> > > and it looks like they could use some realignment too. Obviously not for this fix.
> > > 
> > > git grep -C6 'display-hint.*ipv6$' Documentation/netlink/specs/
> > 
> > The ip6gre spec shows
> > -
> >    name: local
> >    display-hint: ipv6
> > -
> >    name: remote
> >    display-hint: ipv6
> > 
> > The dump result looks good.
> 
> Those two are defined in linkinfo-gre6-attrs, which is declared as a subset-of
> linkinfo-gre-attrs.
> 
> In linkinfo-gre-attrs they are declared as:
> 
> -
>   name: local
>   type: binary
>   display-hint: ipv4-or-v6
> -
>   name: remote
>   type: binary
>   display-hint: ipv4-or-v6
> 
> I have tested with deleting one or the other's display-helper, and at least
> in cli.py, this kind of display-hint overloading works.
> 
> > So for others ipv6 field, what alignment should we
> > use? Should we add checks: min-len: 16? Do we need byte-order: big-endian?
> 
> IPv6 is always big-endian, the marking first becomes needed when/if we make
> them an u128 type. Until then it would just be nice if either all or none
> of them had the big-endian marking.
> 
> I prefer exact-len over min-len. The current tally is:
> 
> $ git grep 'len.*: 16' Documentation/netlink/specs/ | cut -d: -f2- | sed -e 's/^ *//' | sort | uniq -c
>       7 exact-len: 16
>       5 len: 16
>       6 min-len: 16
> (assuming that only IPv6 has a length of 16)
> 
> "len: 16" as used in ovs_flow's ipv6-src and ipv6-dst only works because they
> are struct members, not attributes.

Hmm, I just found that I tried to do that 2 years ago[1] but forgot why I give
up... I saw you have fixed the fou part with 9f9581ba74a9
("netlink: specs: fou: change local-v6/peer-v6 check").

Let's alignment others this time.

[1] https://lore.kernel.org/netdev/20231215035009.498049-4-liuhangbin@gmail.com/

Thanks
Hangbin